Many moth caterpillars have a tough time of it for they attract numerous parasitic insects who infect them. This tiny geometrid has what looks like a wasp cocoon growing out of its back. There are numerous ways in which other insects parasitize caterpillars, but all of them involve the poor caterpillar being a living host for the parasites until they are ready to leave their host, at which point it dies. Tiny parasitic wasps and Tachinid flies are the most common parasitic insects.